The present invention relates generally to equipment utilized and operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a safety valve having a mono spring closure mechanism.
It is desirable to provide a safety valve which has an increased inner diameter/outer diameter ratio. This is due to the restricted confines of a wellbore and the desire to have a large flow area for production of fluids from the wellbore. For these reasons it is also desirable to provide a safety valve closure mechanism which can be accommodated in a reduced thickness sidewall area, while still enabling the safety valve to be effectively and reliably closed when necessary.
In the past, safety valve designers have tried using multiple springs in closure mechanisms, in order to provide sufficient force to operate the closure mechanisms in reduced thickness sidewalls. Some of these designs have been successful. However, the use of multiple springs increases the complexity of a closure mechanism while reducing reliability (due to multiple moving elements, increased possibility that debris could impair operation of one of the elements, etc.) and increasing the cost of the closure mechanism.
Therefore, it may be seen that improvements are needed in the art of safety valve closure mechanisms. It is among the objects of the present invention to provide such improvements.